The primary approaches currently used for measuring in vivo interstitial biological activity, processes, and/or compounds in human or animal subjects require collection of interstitial fluid samples followed by measurement using in vitro assay systems. These approaches generally do not allow for comprehensive detection or measurement of interstitial biological activity, processes, and/or compounds since endogenous regulatory mechanisms are removed. Moreover, such in vitro assay systems do not allow for real-time monitoring or continuous monitoring of interstitial fluid processes in normal or disease states.